Digital tuner

Abstract

A variable rate tuner is one in which the rate of change of tuned frequency with respect to tuning shaft rotation varies automatically as a function of the shaft rotation speed. In this tuner the circuitry is completely digital, including a shaft encoder which puts out shaft velocity and shaft direction signals. A digital multiplier multiplies or divides the shaft velocity signal. A counter selects the multiplication factor as a function of shaft velocity. The multiplied velocity signal then increments or decrements a frequency-determining quantity, depending upon whether the shaft direction is such as to increase or decrease the tuned frequency.

I claim: 
     
       1. A digital variable rate tuner drive circuit comprising: tuning control means, means responsive thereto for providing a rate signal and a direction signal digitally indicating the rate of activity of said control means and the direction of effectiveness of said control means respectively, an incrementable and decrementable digital counter for storing a quantity which determines the frequency of a tuner, a digitally programmable multiplication circuit receiving said rate signal and digitally multiplying said rate signal by a selected factor, means for applying the output of said multiplication circuit for digitally incrementing or decrementing the quantity stored in said digital counter whereby to raise or lower the tuner frequency, means responsive to said direction signal and arranged to cause said multiplication circuit output to increment said counter quantity when said tuning control means is effective in one direction and to decrement said counter quantity when said tuning control means is effective in the opposite direction, and means responsive to said rate signal to program said multiplication circuit to select a multiplication factor which is proportional to said rate signal, whereby the rate of change of tuner frequency is a function of the rate of activity of said control means.   
     
     
       2. A digital variable rate tuner drive circuit comprising: a movable tuning control member, means responsive to said member to provide a velocity signal and a direction signal digitally indicating the velocity of the motion of said control member and the direction of motion of said control member respectively, an incrementable and decrementable digital counter for storing a quantity which determines the frequency of a tuner, a digitally programmable multiplication circuit receiving said velocity signal and digitally multiplying said velocity signal by a selected factor, means for applying the output of said multiplication circuit for digitally incrementing or decrementing the quantity stored in said digital counter whereby to raise or lower the tuner frequency, means responsive to said direction signal and arranged to cause said multiplication circuit output to increment said counter quantity when said tuning control member is moved in one direction and to decrement said counter quantity when said tuning control member is moved in the opposite direction, and means responsive to said velocity signal to program said multiplication circuit to select a multiplication factor which is proportional to said velocity signal, whereby the rate of change of tuner frequency is a function of the rate of displacement of said control member.   
     
     
       3. A circuit as in claim 2 wherein the values of said multiplication factor extend into the fractional range between zero and one when the velocity of said tuning control member is relatively low, and into the range greater than one when said velocity is relatively high. 
     
     
       4. A circuit as in claim 2 further comprising a digital display arranged to read out the numerical content of said counter whereby to provide a running indication of the tuner frequency. 
     
     
       5. A circuit as in claim 2 wherein: said means responsive to said tuning control member comprises a pulse generator means, said velocity signal is a pulse train provided by said pulse generator means at a repetition rate proportional to the control member velocity, said multiplication circuit receives said pulse train and produces an output pulse train at a repetition rate equal to said pulse repetition rate multiplied by said selected factor, and said multiplied repetition rate output pulse train is used to increment or decrement said digital counter quantity.   
     
     
       6. A circuit as in claim 5 wherein said means which programs said multiplication circuit comprises: a second counter for counting the pulses in said velocity signal, and means responsive to the count accumulated in said second counter during a predetermined time interval to program said multiplication circuit to select a multiplication factor which is proportional to said accumulated count, whereby said multiplication factor is proportional to the rate of displacement of said control member.   
     
     
       7. A circuit as in claim 6 wherein said means which programs said multiplication circuit further comprises: means for defining said predetermined time interval and for resetting said second counter to zero at or prior to the beginning of said interval and for starting the count of said second counter at the beginning of said interval and stopping the count of said second counter at the end of said interval, a storage register, and means for loading into said register the count accumulated in said second counter at the end of said interval, said multiplication circuit being responsive to the quantity stored in said register to select the multiplication factor employed by said multiplication circuit.   
     
     
       8. A digital variable rate tuner drive circuit comprising: a tuning control shaft;   a shaft encoder responsive thereto to provide a pulse train signal the repetition rate of which is proportional to the angular velocity of said shaft and a second stream of pulses digitally indicating the angular direction of said shaft, an incrementable and decrementable pulse counter for storing a quantity which determines a tuner frequency;   a digitally programmable multiplication circuit receiving said shaft encoder pulse train and multiplying the repetition rate thereof by a selected factor to produce a multiplied repetition rate output pulse train which is available for incrementing or decrementing the quantity stored in said pulse counter whereby to raise or lower the tuner frequency;   means responsive to said shaft angular direction stream of pulses and arranged to cause said multiplied repetition rate pulse train to increment said pulse counter quantity when said tuning control shaft is turned in one angular direction and to decrement said pulse counter quantity when said tuning control shaft is turned in the opposite angular direction; and   means responsive to said shaft encoder pulse train repetition rate to program said multiplication circuit to select a multiplication factor which is proportional to said shaft angular velocity, whereby the rate of change of the tuner frequency is affected.   
     
     
       9. A circuit as in claim 8 wherein said pulse counter has separate inputs for respectively incrementing and decrementing the quantity therein, and further comprising gating means for steering the multiplied repetition rate pulse train output of said multiplication circuit to a selected one of said pulse counter inputs, and means responsive to said shaft angular direction stream of pulses to cause said gating means to steer said multiplied pulse train to said incrementing input when said tuning control shaft is turned in one angular direction and to said decrementing input when said tuning control shaft is turned in the opposite angular direction. 
     
     
       10. A circuit as in claim 9 wherein said shaft angular direction stream of pulses is produced by said shaft encoder in a selected phase relation to said angular velocity pulse train signal, and further comprising means for detecting the sign of the phase relation between said two shaft encoder outputs whereby to determine the angular direction of said tuning control shaft, said detecting means being arranged to control said gating means whereby to increment or decrement said pulse counter according to said shaft direction.